/Engine/Source/Editor/MaterialEditor/Public/MaterialEditingLibrary.h
Create a new material expression node within the supplied material function
static [UMaterialExpression](API\Runtime\Engine\Materials\UMaterialExpression) * CreateMaterialExpressionInFunction ( [UMaterialFunction](API\Runtime\Engine\Materials\UMaterialFunction) * MaterialFunction, [TSubclassOf](API\Runtime\CoreUObject\Templates\TSubclassOf)< [UMaterialExpression](API\Runtime\Engine\Materials\UMaterialExpression) > ExpressionClass, int32 NodePosX, int32 NodePosY )